Definition
An adverb used throughout legal writing to qualify a standard, obligation, or judgment by reference to what a rational, fair-minded person would consider acceptable under the circumstances. "Reasonably" does not mean perfectly, optimally, or beyond all doubt — it imports a middle ground between extremes, calibrated to context.
In legal usage, "reasonably" performs two distinct functions:
1. As a standard of conduct: "Reasonably" modifies what a person was required to do or refrain from doing. A party must act as a reasonably prudent person would under like circumstances. This is the workhorse of tort law, contract law, and administrative reasonableness review. The question is not what the party actually believed or intended, but what an objectively reasonable actor would have done.
2. As a qualifier of degree or amount: "Reasonably" limits a quantity, scope, or duration to what is proportionate and defensible — as in "reasonable attorney's fees," "reasonable time," or "reasonable royalty." Here the word functions less as a behavioral standard and more as a proportionality constraint, asking whether a measure or figure falls within an acceptable range.
Because "reasonably" is a relational term — it always modifies something else — it has no fixed legal content standing alone. Its meaning is derived from the noun or verb it qualifies and the legal context in which it appears.
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Common Language
Modern common usage (Wiktionary): In accordance with reason; fairly; satisfactorily; not extremely.
Historical common usage (Webster's 1913): In a reasonable manner; moderately; tolerably.
The gap between common and legal meaning is one of precision, not direction. Colloquially, "reasonably" is a hedge — it signals approximation and informality. In law, it is a term of art imposing an objective standard of conduct or a judicially reviewable constraint on degree. When a contract requires performance within a "reasonable time" or a tort claim turns on whether a defendant acted "reasonably," courts are not asking whether the result was merely tolerable. They are invoking an objective benchmark — what a prudent, similarly situated person would do — that carries enforceable consequences. The apparent similarity between common and legal usage masks this shift from subjective tolerance to objective accountability.
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Common Confusion
"Reasonably" is frequently conflated with "in good faith." Both qualify conduct by reference to internal acceptability, but they measure different things. Good faith looks inward — it asks whether the party acted honestly and without intent to deceive. Reasonably looks outward — it asks whether the conduct matched an objective external standard, regardless of the party's subjective honesty. A person can act in good faith and still fail to act reasonably; conversely, objectively reasonable conduct can, in rare circumstances, coexist with bad faith. Many legal standards require both, and researchers should not assume one satisfies the other.
"Reasonably" is also sometimes misread as equivalent to "substantially." Substantial performance and reasonable conduct are related but distinct concepts. Substantial measures the degree of completion; reasonable measures the quality and propriety of conduct.
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Why It Matters in Research
"Reasonably" is one of the most widely distributed words in Anglo-American legal writing, which creates specific research hazards.
First, context controls meaning. The word appears in tort standards (reasonable care), contract law (reasonable time, reasonable efforts), attorney's fees jurisprudence (reasonable hours, reasonable rates), trade secret law (reasonable measures to maintain secrecy), constitutional law (reasonable suspicion, reasonable search), and administrative law (arbitrary and capricious review, which often tracks reasonableness). Each context has developed its own body of doctrine. A case interpreting "reasonably" in a trade secret context will not govern what "reasonably" means in a fee award calculation.
Second, the objective/subjective distinction is critical. In some legal contexts, "reasonably" imports a pure objective standard — what a hypothetical reasonable person would do. In others, courts blend objectivity with the defendant's particular circumstances (age, disability, professional expertise). Historical sources do not always flag which version applies, and the distinction has shifted over time.
Third, Bouvier's treatment is thin. Bouvier cites a Kentucky case for the proposition that "reasonably" means "moderately or tolerably" — a common-usage gloss that understates the term's legal function. Researchers relying solely on Bouvier's entry will miss the objective-standard architecture that modern doctrine has built around this word.
Fourth, compound constructions matter enormously. "Reasonably prudent," "reasonably foreseeable," "reasonably necessary," "reasonably equivalent value" — each is a distinct legal term with its own doctrinal development. Never treat "reasonably" as interchangeable across these compounds.
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Historical Dictionary Support
Bouvier's defines "reasonably" as "a qualifying word" meaning "moderately or tolerably," citing a Kentucky appellate decision for that reading. The definition accurately captures the word's general sense but offers no analytical framework for its legal operation. Bouvier does not address the objective-standard function, the distinction between conduct standards and degree qualifiers, or jurisdictional variation in how courts apply reasonableness tests.
Webster's 1913 and Wiktionary are largely aligned with Bouvier on common meaning, reinforcing that historical legal dictionaries tracked ordinary usage rather than developing a distinctively legal account of the term. This convergence is itself informative: "reasonably" entered legal writing from ordinary English and was given normative legal weight through judicial elaboration, not lexicographic definition. The doctrinal substance of "reasonably" lives in case law and treatise commentary, not in dictionary entries.
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Jurisdictional Note
Federal and state courts universally employ reasonableness standards, but the content of those standards varies by jurisdiction and legal domain. The reasonable person in negligence law, the reasonable rate in fee-shifting statutes, and the reasonable measures required for trade secret protection each have jurisdiction-specific content shaped by local case law. Federal courts applying state tort law must use state-law reasonableness standards; federal statutory reasonableness standards are governed by federal law.
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Encyclopedia Cross-Reference
The Law Mind Torts & Personal Injury Encyclopedia — Negligence: The Reasonable Person Standard
The Law Mind Remedies & Equity Encyclopedia — The Lodestar Method: Reasonable Hours x Reasonable Rate (Hensley v. Eckerhart)
The Law Mind Intellectual Property Encyclopedia — Reasonable Measures to Maintain Secrecy
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